where \(B_n\)  is the \(n\) -th complete exponential Bell polynomial [1]} and \(B_0=1\) .
Thus, \(Z_N\)  in 2D is fully determined by a dimentionless parameter \(G_{2D}\)  and rises monotonically from \(Z_0=1\)  to \(Z_\infty =\exp (G_{2D}\zeta (2))\) , where \(\zeta (2)\)  is the value of the zeta function at 2.
